1. Field of the Invention
The present invention relates to a sheet transport device transporting a sheet via a predetermined transport path. This invention is applicable particularly to an image reading apparatus such as a facsimile and photocopier; however, its application is not limited to the above cases, and the invention is useful for other types of apparatuses.
2. Description of the Related Art
The sheet transport device transports a sheet from a sheet tray to a discharge tray via a transport path. The discharge tray is attached to a main body of the sheet transport device with a hinge member for the purpose of downsizing the device. The discharge tray is bent toward the device main body when the sheet transport device is not in use and is so opened as to retain the sheet when using the sheet transport device.
A sheet tray wherein an auxiliary tray is coupled rotatably thereto with a hinge member which is formed of a projection member made from an elastic material and a bearing has been known. The auxiliary tray comes off the sheet tray because of elastic deformation of the projection member when an impact or a load larger than a bearable load is applied on the auxiliary tray. Therefore, the auxiliary tray is not damaged even when impact or load larger than the bearable load is applied on the auxiliary tray. Also, the projection member returns to its original shape without being damaged. The auxiliary tray is attached again to the sheet tray by the use of the projection member.
A sheet tray provided with an extension tray which is rotatable about a main tray has been known. When the extension tray is opened, it is possible to house a sheet having a size larger than the main tray. The sheet tray is compact in size when the extension tray is closed.
A sheet feeding device feeding a recording paper placed on a sheet tray to an image forming device through a sheet feed opening, which is provided with a cover member rotating in such a fashion as to open and close the sheet feed opening has been known. The cover member prevents entry of contaminants through the sheet feed opening.
The above technologies are disclosed in JP-A-10-167547 published on Jun. 23, 1998, JP-A-2003-201054 published on Jul. 15, 2003, and JP-A-2002-2975 published on Jan. 9, 2002.
A footprint of the sheet transport device is reduced when the discharge tray is capable of opening/closing and closed in such a fashion as not to project from the device when the device is not in use. The discharge tray is prevented from being damaged when the discharge tray is capable of coming off the device main body when an excessive force is applied on the discharge tray. The discharge tray may come off by an external force when the discharge tray is closed. However, when the discharge tray is closed, it is unlikely that the discharge tray will be damaged. It is undesirable that the discharge tray comes off when the discharge tray is closed.
An opening other than the sheet feed opening connecting to an internal portion of the device is formed on a housing of the sheet transport device for various purposes. Contaminants may enter the internal portion of the device through the opening. Particularly, if the contaminants are fallen on a control substrate, an electrical failure can be caused by the contaminants. Various electrical wirings are connected to the control substrate. In view of assembly of the wirings and the like, it is undesirable to cover the control substrate with a cover before finishing the wirings.